DYNACO Stereo-400
Released in 1972
Stereo-400MA : ¥ 319,800 (around 1976)
Stereo-400 : ¥ 289,500 (around 1976)
Commentary
High power stereo power amplifier with large power transformer.
There were two types, the Stereo 400 ma with an output meter and the Stereo 400 without a meter.
The circuit configuration consists of emitter-follower circuit for impedance matching, OCL complete complimentary service circuit for all stages of differential-amplified main section, and protection circuit for protecting speakers and amplifiers.
In addition, an element with excellent bare characteristics is used for the driver stage, and the output stage is operated as class A at low output and class AB at high output to eliminate notch distortion at low output.
2500cm2By using a large heat sink, the temperature rise of the output-transistor is prevented. In addition, a Dynabias circuit using ICs is installed to compensate for temperature rise.
The speaker protection circuit consists of three stages : a dynaguard circuit, which is a type of power limiter, a speaker protection fuse, and a pure electronic DC detection circuit, in which when DC voltage is detected at the output, a relay operates to disconnect the speaker from the amplifier.
The Dynaguard circuit is a variable dynamic power limiter that protects the speaker and allows you to select 20, 40, 80, 120W or off (maximum output) depending on the speaker's allowable input.
The amplifier protection circuit uses a voltage / current detection protection circuit for the output transistor, a thermal sensor to protect the transistor from abnormal heat generation, a circuit breaker installed on the AC power line, and a protective fuse for the DC power line.
The output meter mounted on the Stereo 400 ma has an excellent instantaneous response meter directly connected to the output, and the 4-step sensitivity selector switch enables accurate reading.
.JPG)
Model Rating
| Type | Stereo power amplifier |
| Effective power | Double-Channel Drive : 300W + 300W (20 Hz ~ 20 kHz, 4 Ω Load) 200W + 200W (20 Hz to 20 kHz, 8 Ω load) Monaural : 600W (20 Hz ~ 20 kHz, 8 Ω load) |
| Harmonic distortion factor | 0.25% or Less (20 Hz to 20 kHz, Both Channels Driven, Rated Output) |
| Cross modulation distortion factor | 0.1% (Both Channel Drive, 8 Ω) |
| Output bandwidth | 5 Hz ~ 35 kHz (8 Ω load at 100W output) |
| Frequency characteristics (8 Ω load at 1W output) | 8 Hz to 50 kHz + 0 -1dB 10 Hz ~ 50 kHz + 0 -1dB (Stereo-400, 1974 catalog) |
| Input sensitivity | 1.6 V (at rated output) |
| Input impedance | 50k Ω |
| Signal-to-noise ratio | 100 dB or More (8 μ V - Input Short at Rated Output) 106 dB or more (at rated output, according to Stereo-400, 1974 catalog) |
| Waveform rise time | 8 V / μ S |
| Slew rate | 20 V / μ s (Stereo-400, 1974 catalog) |
| Filter | 50 Hz, -12dB/oct. 15 kHz, -12dB/oct. |
| Attachment mechanism | Output Meter (4-Step Sensitivity Switching, Stereo-400MA Only) Input level control Dynaguard (power limiter) |
| Pwer | 100 VAC, 50Hz/60Hz |
| Power consumption | 120W (minimum) 1,100W maximum |
| External dimensions | Width 432x Height 178x Depth 356 mm |
| Weight | 25kg 30 kg (Stereo-400, 1974 catalog) |
| Sold Separately | Fan Kit FAN-1 (¥ 14,500) Output Meter Kit MC-4 (¥ 34,500) Monaural conversion MBI-400 (¥ 14,500) |